1. Field of the Invention
This invention relates to a mimeographic printing machine having a rotary cylindrical drum of an ink-leak-free structure
2. Description of the Related Art
A mimeographic printing machine is currently known which includes a rotary cylindrical drum with an ink supply means located inside an ink-penetrable tubular wall, and a press roller located outside said cylindrical drum. For printing, a stencil is wound on the outer circumferential surface of the tubular wall of the cylindrical drum, whereupon the cylindrical drum is driven to rotate while a paper sheet is supplied between the cylindrical drum and the press roller. While the paper sheet is being moved as held between the cylindrical drum and the press roller, ink is transferred to the paper sheet through the tubular wall and pores of the stencil. Thus an image formed by the pores is printed on the paper sheet.
During the above printing, the ink supplied from the inner circumferential surface of the cylindrical drum passes the pores of the stencil and are then transferred to the paper sheet, thus being consumed little by little. At the trailing end portion of the stencil off the printing area, since there is no pore, excessive ink would accumulate between the outer circumferential surface of the cylindrical drum and the stencil. In this state, continued printing of many paper sheets increases an amount of collected excessive ink. In addition to this, the ink is pushed off gradually to the trailing end portion of the stencil by the squeezing action of the press roller, and finally, the ink would overflow off the trailing end portion of the stencil to make the machine portions around dirty. This phenomenon is commonly called "tail end leakage".